How does Calibre's new kepub conversion compare to Patrick Gaskin's kepubify?

RDavidson · 03-21-2025, 01:57 PM

I'm accustomed to using Patrick Gaskin's kepubify tool for conversions; I even wrote a barebones Calibre plugin to let me run it on epubs in my library and import the resulting kepub.

Now I see Calibre 8 has a kepubify feature built in, but it is built from scratch in Python, rather than using the existing kepubify tool.

How do the two kepub conversion tools compare? Is there any reason other than convenience to use Calibre's tool?

DNSB · 03-21-2025, 09:39 PM

As near as I can tell, both kepub conversion tools output very similar code. I haven't compared the conversion code in the original Kobo Touch Extended driver to that used by Kovid Goyal in calibre's builtin conversion so can't say how much was re-used. I did check for some errors that were generated by the KTE driver conversion and the code in calibre 8.01 did not generate the same errors.

Personally, I use ePub for any books that do not have hi-res graphics that I might want to zoom so will leave the Use Kobo viewer for EPUB books option unchecked for now. Perhaps the next Kobo firmware revision will have me revisiting that decision.

kovidgoyal · 03-21-2025, 09:48 PM

calibre's conversion does many things kepubify does not. Off the top of my head:

1) It does proper sentence detection based on language rules using the ICU library with support for the actual language metadata used in the HTML
2) It includes the kobo.js file by default
3) It has a more extensive test suite
4) It can both add and remove kepub markup
5) Various minor things you would need to read the code to find

And finally since calibre will be used by many more people for many more books, over time the code will become much more robust

npr · 04-03-2025, 07:14 AM

Is there a way to stop kobo.js being added to a book by default?

kovidgoyal · 04-03-2025, 07:44 AM

Quote:

Originally Posted by npr

Is there a way to stop kobo.js being added to a book by default?

Why would you want to?

npr · 04-03-2025, 09:27 AM

I've been converting epubs to kepubs on transfer to the reader for many years mainly using the touch extended driver.
I've never had kobo.js added to my books and being called from every html file in the book so don't see why I need it now. I've spent a lot of time searching for information on kobo.js and found very little so if anyone can add compelling reasons to use this java script I would very much like to hear.

kovidgoyal · 04-03-2025, 09:30 AM

KEPUB's produced by kobo have it. What it's used for you'd have to ask Kobo. And having it in your KEPUBs does not harm anything. Of course if it offends your sensibilities, for some reason, feel free to stick with calibre 7 and use KTE.

npr · 04-03-2025, 10:01 AM

Would you consider not adding the java script if "Enable/disable hyphenation" is not ticked and "modify CSS is not ticked? In this case nothing needs adding to the <head> of each file.

JSWolf · 04-03-2025, 11:53 AM

Quote:

Originally Posted by npr

Would you consider not adding the java script if "Enable/disable hyphenation" is not ticked and "modify CSS is not ticked? In this case nothing needs adding to the <head> of each file.

Hyphenation doesn't need to be added to each HTML. What's needed to to make a single hyphenation.css file. That's al that's needed.

JSWolf · 04-03-2025, 11:53 AM

Quote:

Originally Posted by kovidgoyal

KEPUB's produced by kobo have it. What it's used for you'd have to ask Kobo. And having it in your KEPUBs does not harm anything. Of course if it offends your sensibilities, for some reason, feel free to stick with calibre 7 and use KTE.

Would you please move the hyphenation code from each HTML file to a hyphenation.css file? Thanks.

kovidgoyal · 04-03-2025, 10:02 PM

Quote:

Originally Posted by npr

Would you consider not adding the java script if "Enable/disable hyphenation" is not ticked and "modify CSS is not ticked? In this case nothing needs adding to the <head> of each file.

No, that's just a weird and unintuitive side effect. Neither of those settings have anything to do with the javascript. Oh and actually, I just remembered, you can prevent it from being added by overwriting kobo.js in your settings using the mechanism described in: https://manual.calibre-ebook.com/cus...ates-et-cetera

You can replace kobo.js with an empty file.

npr · 04-04-2025, 07:38 AM

Thanks, I now have a empty "kobo.js" file in my books I'll settle for that.

03-21-2025, 01:57 PM	#1
RDavidson Member Posts: 11 Karma: 139288 Join Date: May 2017 Device: Kindle Voyage, Kobo Clara HD	How does Calibre's new kepub conversion compare to Patrick Gaskin's kepubify? I'm accustomed to using Patrick Gaskin's kepubify tool for conversions; I even wrote a barebones Calibre plugin to let me run it on epubs in my library and import the resulting kepub. Now I see Calibre 8 has a kepubify feature built in, but it is built from scratch in Python, rather than using the existing kepubify tool. How do the two kepub conversion tools compare? Is there any reason other than convenience to use Calibre's tool?

03-21-2025, 09:48 PM	#3
kovidgoyal creator of calibre Posts: 45,116 Karma: 27110892 Join Date: Oct 2006 Location: Mumbai, India Device: Various	calibre's conversion does many things kepubify does not. Off the top of my head: 1) It does proper sentence detection based on language rules using the ICU library with support for the actual language metadata used in the HTML 2) It includes the kobo.js file by default 3) It has a more extensive test suite 4) It can both add and remove kepub markup 5) Various minor things you would need to read the code to find And finally since calibre will be used by many more people for many more books, over time the code will become much more robust Last edited by kovidgoyal; 03-21-2025 at 10:38 PM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
kepubify v3: A fast, standalone EPUB to KEPUB converter (plus covergen/seriesmeta)	geek1011	Kobo Reader	227	07-29-2023 11:25 AM
Little bit confused about Kepub conversion in Calibre	jaceneliot	Plugins	3	03-06-2023 01:37 PM
kepub conversion not available on calibre 5.2(64bit)	alexstacey	Kobo Reader	4	10-07-2020 07:11 PM
Calibre 2.68 - kepub conversion no longer available?	kyrilson	Calibre	3	09-23-2016 06:06 AM
Aura HD Conversion of EPUB to KEPUB using Calibre	kmack9	Kobo Reader	15	09-08-2013 01:00 PM

03-21-2025, 09:39 PM	#2
DNSB Bibliophagist Posts: 44,165 Karma: 165572332 Join Date: Jul 2010 Location: Vancouver Device: Kobo Sage, Libra Colour, Lenovo M8 FHD, Paperwhite 4, Tolino epos	As near as I can tell, both kepub conversion tools output very similar code. I haven't compared the conversion code in the original Kobo Touch Extended driver to that used by Kovid Goyal in calibre's builtin conversion so can't say how much was re-used. I did check for some errors that were generated by the KTE driver conversion and the code in calibre 8.01 did not generate the same errors. Personally, I use ePub for any books that do not have hi-res graphics that I might want to zoom so will leave the Use Kobo viewer for EPUB books option unchecked for now. Perhaps the next Kobo firmware revision will have me revisiting that decision.

04-03-2025, 07:14 AM	#4
npr Zealot Posts: 113 Karma: 37418 Join Date: Jan 2013 Device: H2OE2, Libra 2	Is there a way to stop kobo.js being added to a book by default?

04-03-2025, 09:27 AM	#6
npr Zealot Posts: 113 Karma: 37418 Join Date: Jan 2013 Device: H2OE2, Libra 2	I've been converting epubs to kepubs on transfer to the reader for many years mainly using the touch extended driver. I've never had kobo.js added to my books and being called from every html file in the book so don't see why I need it now. I've spent a lot of time searching for information on kobo.js and found very little so if anyone can add compelling reasons to use this java script I would very much like to hear.

04-03-2025, 09:30 AM	#7
kovidgoyal creator of calibre Posts: 45,116 Karma: 27110892 Join Date: Oct 2006 Location: Mumbai, India Device: Various	KEPUB's produced by kobo have it. What it's used for you'd have to ask Kobo. And having it in your KEPUBs does not harm anything. Of course if it offends your sensibilities, for some reason, feel free to stick with calibre 7 and use KTE.

04-03-2025, 10:01 AM	#8
npr Zealot Posts: 113 Karma: 37418 Join Date: Jan 2013 Device: H2OE2, Libra 2	Would you consider not adding the java script if "Enable/disable hyphenation" is not ticked and "modify CSS is not ticked? In this case nothing needs adding to the <head> of each file.

04-04-2025, 07:38 AM	#12
npr Zealot Posts: 113 Karma: 37418 Join Date: Jan 2013 Device: H2OE2, Libra 2	Thanks, I now have a empty "kobo.js" file in my books I'll settle for that.

Advert

Advert